p>Are these claims true? National inventories are submitted to the United Nations Framework Convention on Climate Change (UNFCCC) by developed countries' environmental agencies or ministries. The latest available inventories show that CO2 emissions rose 5.9% in the EU from 1997-2004, while they rose 7.3% during the same timeframe in the United States (the national inventories submitted by the EU are for the original 15 member countries). So according to the best data we have, the US did not outperform the EU during the Kyoto time period.

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p>But the Bush Administration's claim is technically true. As shown on the chart below, CO2 emissions in the EU grew 4.5% from 2000-2004, while they only grew 2.1% in the US. This growth is likely due to the mild economic recession in 2001 and the economic impacts of September 11th.

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p>However, this claim is problematic. As with any data, one time series may tell a very different story than another time series. Consider this: while US emissions grew slower than the EU from 2000-2004, the US growth rate was well above the EU from 2001-2004: or for that matter, from 2002 or 2003. A single year can make a big difference in interpreting trend data.

In reality, all of these time series are too narrow for useful analyses. For this reason, the most common timeframe is 1990 to the present, or the most recent year for which there is data. 1990 is used partly because it coincides with the baseline for the Kyoto Protocol, and partly because the longer time period discounts short-term changes that may not signal a broader trend. And as these two charts show, CO2 emissions in the US have risen much faster than the EU's from 1990-2004, both in percentage growth and in total metric tons.